Aircraft typically include a plurality of flight control surfaces that, when controllably positioned, guide the movement of the aircraft from one destination to another. The number and type of flight control surfaces included in an aircraft may vary depending, for example, on whether the aircraft is a fixed-wing or rotary-wing aircraft. For example, most fixed-wing aircraft typically include primary flight control surfaces, such as a pair of elevators, a rudder, and a pair of ailerons, to control aircraft movement in the pitch, yaw, and roll axes. Aircraft movement of rotary-wing aircraft in the pitch, yaw, and roll axes is typically controlled by via movement of the rotating aircraft rotors, and may additionally be controlled via movement of one or more flight control surfaces.
The positions of the aircraft flight control surfaces and/or rotors are typically controlled via a flight control system. The flight control system, in response to position commands that originate from either the flight crew or an aircraft autopilot, moves the aircraft flight control surfaces and/or rotors to the commanded positions. In most instances, this movement is effected via actuators that are coupled to the flight control surfaces. Typically, the position commands that originate from the flight crew are supplied via one or more inceptors. For example, many fixed-wing aircraft include a plurality of inceptors, such as yokes or side sticks and rudder pedals, one set each for the pilot and for the co-pilot, and many rotary-wing aircraft include one or more of a cyclic, a collective, and rudder pedals.
In fly-by-wire flight control systems, the inceptors are inherently disconnected from the aircraft flight control surfaces because, unlike traditional flight control systems, there is no mechanical link between the inceptor and the flight control surfaces. As a result, it is postulated that pilots could introduce control inputs to the inceptor that exceed the response capabilities of the one or more portions of the flight control system. If such a postulated event were to occur, a pilot may exaggerate the control input, which can in turn result in what is known as pilot induced oscillations (PIO). This form of PIO is generally known as Category II PIO or non-linear PIO.
Hence, there is a need for a flight control system and/or inceptor that prevents, or at least reduces the likelihood of, pilot induced oscillations. The present invention addresses at least this need.